The National Enquirer recently reported that the Home Alone star has a $6,000-a-month habit and has turned his Manhattan home into a 'drug den'.
The article - under the headline 'Six Months To Live' - alleged that he is addicted to heroin and painkiller oxycodone, dubbed hillbilly heroin.
Culkin's publicist Michelle Bega told TMZ that the story is "not only categorically without merit, but it is also impossibly and ridiculously fictitious".
He added: "We beseech the responsible media to consider the source and its reputation and to please not perpetuate this destructive and insulting story by pursuing it any further."
Culkin's spokesperson was previously forced to deny reports of his ill health in February after pictures of the 31-year-old looking dishevelled with a can of Red Bull in his hand began circulating online.